As is known in the art, the oil lubrication of pistons in internal combustion engines, such as automotive engines, may be less than optimum in particular situations and under certain engine operating conditions. A lack of optimum levels of lubrication around portions of the piston or skirt periphery can lead to increased piston noise as well as increased friction, in severe cases leading to increased chance of scoring of the piston skin and cylinder liner or wall. Less than optimum lubrication can result in increased piston noise independent of scuffing, scoring and wear issues.
A greater portion of the side stress developed during piston operation is known to occur in regions referred to as the thrust faces. The thrust faces are located on opposing sides of the piston and skirt and aligned perpendicularly to the ends of the piston pin bore. During fuel combustion in the power stroke, side thrust loads become concentrated at the thrust faces. As is known in the art, these high stress regions are subject to greater pressure and frictional force developed against the cylinder wall resulting in increased operating noise and ultimately to greater wear.